1. Field of the Invention
The present invention relates to an automatic melt supplying method and a holding furnace having an automatc melt supplying system which, though simple, are capable of accurate melt supply under a severe, high-temperature condition.
2. Description of the Prior Art
The holding furnace generally comprises a holding chamber, and a melt supplying chamber communicating with the holding chamber. The holding chamber receives molten aluminum or various other non-ferrous metals through a melt inlet, and maintains the melt at a predetermined temperature by use of a heater or a burner. The melt supplying chamber is connected to a casting machine, and supplies a fixed amount of molten non-ferrous metal for every casting operation.
In the conventional holding furnace, the holding chamber is constructed fluid-tight and includes various sensors. This holding chamber is pressurized to cause the fixed amount of melt to be supplied from the melt supplying chamber to the casting machine. Such a complicated construction is placed under an extremely high temperature condition and perfect fluid-tightness cannot be assured, which make the holding furnace difficult to control in a satisfactory manner. This results in a low melt supplying precision and is a primary cause of casting machine malfunctioning and defective products.
Such a pressurization/non-pressurization switching mode requires a compressor, sensors, control devices, and a separate melt supplying machine which takes up a large space. Further, when the melt is supplied under pressure, the melt surface becomes ruffled to a great extent thereby entraining oxides in an increased amount and impairing product quality. Where the melt is scooped with ladles, coating materials fall from the ladles into the melt to add impurities to the melt. Thus, the conventional holding furnace has various drawbacks.